Phase-balancing system



Feb. 14,- 1928. 1,658,906

J. SLEPIAN PHASE BALANCING SYSTEM Filed June 10, 1922 5 Sheets-Sheet l gt f m 1-792. Fly. 3.

WITNESSES: INVENTOR Jase 2h Slepian.

Feb. 14, 1928.

1,658,906 J. SLEPIAN PHASE BALANCING SYSTEM Filed June 10, 1922 3 Sheets-Sheet 2 '/0 WITNESSES:

INVENTOR Jbseph Slep/an.

, ATTQRNEY Feb. 14, 1928.

J. SLEPIAN PHASE BALANCING SYSTEM 3 Sheets-Sheet 3 Filed June 10, 1922 nnnnunn INVEN'IZOR Jbs cywh Slepmn.

WITNESSES: I

ATTORNEY Patented Feb. 14, 1928.

l fj

Parent JGSEPH SLEPIAH, OF SW'ISELVALE, PENNSYLVANIA, ASSEGITOR TO WESTINGHOUSE ELECTREC 5 Ii-IAYNUFACTURING CGMFANY, A CORPJRATIOII OF PENNSYLVANIA.

PHASE-BALANCING SYSTEM.

Application filed June 10, 1822. Serial No. 567,449.

My invention relates to phase-balancing systems and it has particular relation to such systems employing single-phase synchronous condensers for effectinga phase balance. 7

in an unbalanced three-phase lino. it the star voltages in the respective phases could be independently regulated and all made numerically equal one to another, the line would not necessarily be balanced because the voltages would not necessarily have a 120 phase displacement. it, however, the delta voltages are made to be equal in magnitude, an equilateral triangle oi electromet'iYG forces results which assures av 120 phase displacen'ient between the respective pl 'lSGS. (Jr, in generah it th'e delta single-phase components of any triangle oit electromotive forces be caused to have any predetermined relationship in magnitude, the various phase relationships ot' the volts" s are absolutely dependent upon such preieterminenl rehu tionship.

Cine ot' the objects of my invention, therefore, is to provide a system wherein the respective single-phase components of the delta voltages across three line conductors ot' a polyphase system are independently regulated in such manner as to provide an equality or any other predetermined relationship between the magnitudes of the various single-phase delta voltages.

A further object of my invention is to provide a systen'i of distribution comprising;

balanced three-phase line having three depeudent single-phase loads connected thereto and three single'phase synchronous condensers connected across 'd loads and regulated to maintain a constant voltage.

3:. still further object of my invention is to provide a system utilizing three sin phase synchronous machines for phase ancing in which the l'ieating of the machines is reduced by means of interconnected damper windings.

A still further object of my invention is to provide system in which the major portion of a balancing load is carried by a polyphase shunt balancing machine and the ubalaucing ett'ects of the internal impedance of said machine are counteracted by means of serially connected single-hhase synchronous condensers regulated for constant line voltages.

With these and other objects in view, my in ention consists in the methods and apparatus pointed out in the following description and illust'ated in the accompanying drawing wherein V Figure 1 is a diagrammatic view of apparatus and circuits embodyingmy invention in a simple form.

Figs. 2, 3 and are vector diagrams illus trating the current and voltage relationships, and

Figs. and; 6 are diagrammatic views showing modified embodiments of my inyention.

1n the form of my invention shown in l, a three-phase source 7 supplies power to a three-phase transmission line 8, 9 and 10. Feeders 11, 12 and 13 are connected to the various delta phases oi said line to supply independent single-phase loads 14;, 15 and 16, respectively. which may be sections of a single-phase railway system or systems. for example. For simplicity of illustration the steparp and stepdown transformers which would ordinarily be employed in practice are not shown.

Across each of the teeders 11, 12 and 13 is connected asingle-phase synchronous con denser, said condensers beingdiagrammath cally indicated at 1. 18 and 19. respectively, and being provided with direct current exciting windings which are energized trom exciters 20, 21 and respectively. Any suitable form of voltage regulator is employed, as indicated at 23. 2d and respectively, for holdingthe voltage at the terminal of each synchronous condenser at any constant predetermined value.

The operation of the system just described will best be understood by reference to Figs. 2. 3 and It will be understood that the unbalanced current drawn by the three independent single-phase loads l l. 1.5 and 16 may be resolved into a. forwardly rotating major component and a backwardly rotating minor component 01 balanced currents. The bac wardly rotating component, which is the unbalancing; component. is illustrated in Fig.

2 as a balanced system of star vectors, a, b and 0.

In order to neutralize the unbalancing effect of the single-phase loads it is, therefore, necessary for the synchronous condensers 17, 18 and 19 to draw from the line equal and opposite currents indicated, in Fig. 3, by the vectors a, b and 0.

' If the forwardly rotating voltage vectors are represented by the star voltages A, B

and C in'Fi and thewbackwardl ro- A, B and C.

In order to cause the currents drawn by the respectivemachines to fall in said lines, a circulating current willbe established in the delta circuit comprising the feeders 11,

12 and 13,-the primary windings of the ma-' chines 17, 18 and 19 and the intervening ortions of the transmission line 8- 9 and P 7 .10. The circulating current just mentioned willappear as zero-phase-sequence current comprising vectors aa, 5'7) and cc .which are equal in magnitude and parallel one to another.

By taking the resultant of the vectors justv mentioned and the corresponding vectors a, Z) and 0, respectively, it will be found that currents 0a, 0?) and 00 may be drawn which are in phase relationship to the corresponding voltage vectors, thus proving that the unbalanced load currentsv may be balanced by means of purely wattless currents drawn by the respective single phase machines, of which one component is a Zei'ohaSe-sequence current circulating around the, delta-connected primary windings of the three machineslVhile I have illustrated the vectors as star vectors for facility of illustration, it. is obvious that the same demonstration applies 'to the delta quantities, as the same vectors may be employed to form the delta diagram.

A little reflection will show that the particular conditions illustrated in Fig; 4, where-- in the vector representing the circulating zero-phase-sequence currents is in phase with one of the load-currentvectors, namely, 00.

represents an extreme case in which one of the single-phase machines is carrying a maximum current which is twice the current corresponding to the negative-phasesequence or unbalancing load current, while the other two single-phase machines are each carrying a'current equal to said component.

In Fig. 5, I have shown an arrangement whereby the zero-phase-sequence eirculating currents may be avoided, thereby reducing the heating in the individual machines- It will be noted that the circulating currents were inaugurated byreason of the requ1reinent that the currents drawn by the machines should be entirely wattless, either leading or lagging. If, however, power is interchanged between the three machines, the. currents drawn by the primary windings thereof may be made substantially equal to the currents represented by the vectors a, Z) and 0', thus rcducing'the heating,- as above mentioned.

Since the single-phase current in the primary winding of each machine produces two equal fields rotating in opposite directions, and one of said fields produces the currents circulating in the damper windings of the machine, it'is evident thatthe relative magnitudes of the primary currents'in the three machines may be controlled by controlling the relative magnitudes of the circulating damper currents in the respective machines. In Fig. 5 is shown a system inwhich the respective machines 17, 18 and 19 are provided with wound damper windings 26, 27 and 28, respectively, which are connected. through suitable slip rings 29, 30, 31 and 32, to form series closed-circuit such that the current in each phase of each damper winding must pass through the corresponding phases of the other damper windings. With this arrangement, the operation of the voltage regulators 23, 24: and 25 maintaining the respective voltages equal and con stant, causes each machine to draw current or" the proper phase and magnitude to neutralize the unbalancing component currents in the transmission line 8, 9, 10.

As the aggregate of the three single phase machines 17, 18 and 19 of Fig. -5 is about 10%, larger in size than a single polyphase machine of the same k. v. a. rating, it may be desirable, under some circumstances, to

employ an ordinary polyphase shuntconnected phase balancer to perform the major portion of the balancing operation, utilizing-- the single-phase machines merely as means for overcoming theunbalancing effect of the internal in'ipedance-drops.in the shunt balancer. V r

in Fig. 6, I have illustrated such a system wherein a shunt balancer machine 33 has a three-phase primary winding 34, 35, 36said windings being serially connected, respectively, with the primary windings of the single-phase machines 17", 18 and 19 the whole being connected in delta across the transmission line 8, 9, 10. The single-phase machines 17", 18", 19 in this case may be very small, ch machine merely develops enough electromotive force to compensate for the impedance losses of the shunt balancer 33, the magnitude of the voltages being controlled by means of the voltage regulators 23, and 25 which are each connected to respond the corresponding line voltages, a in the preceding figures.

somewhat related system utilizing induction regulators for balancing the voltages in a three-phase line is shown and claimed in 4 co-pending application, Serial No. i430, liled sii'nultaneously *ith the present appl 'on and patented August 2', 1925, Ho. LooldlTO.

ll hile l have deem bod certain characteroi, my invention in detail, therefore, have pointed out certain of the nest obvious principles and purposes there- W i ad that the language empic ed in the following claims shall be limited to the precise features described, but I intend that the i s shall be construed to cover all modifications which are fairly comn'ehended by the language thereof, when read in connection with the prior art, re 'ardless of the details and functions mere tioned in the description or illustrated in the dra ving.

it claim as my invention:

1. i pelyphase system comprising a polyye generator, a polyphase transmission s(;ti:lt@( therewith, a plurality of inidently variable single-phase load deconnected across different phases of delta phases of said transmission line, volta econtrolling means including i e-phase devices of which the imiedance has a reactive component connected in shunt across said delta phases of said line, and means for so varying the reactive components of said devices as to maintain predetermined relative magnitudes of the three singlephase voltages of said delta.

A polypliase system comprising a polyplmse generator, a polyphase transmission line associated therewith, a plurality of inlf:"C-il(lft11tl J ariable single-phase load de- "es connected across dillerent phases of ransm sion line at points remote from said generator, and voltage-controlling means including three single-phase devices of which the impedance has a reactive component connected in shunt across delta pl ases of said line at points remote from said generator, and means for so varying the reactive components of said devices as to maintain a predetermined relation between the magnitudes of the voltages in said delta.

A three-phase system comprising a subutially balanced three-phase generator, a hree-phase transmission line associated therewith, a plurality of independently vari single-phase load devices connected oss diti'erent phases of said transmission line, three single-phase devices of which the in'ipedancc has a reactive component connected in shunt across delta phases of said line, and means for so varying the reactive components of said devices as to neutralize unbalancing eliect ct said single-phase load devices.

a. A three-phase system comprising a substantially balanced three-phase generator, a three-phase transmission line associated therewith, aplurality of independently variable single-phase load devices connected across difi'erent phases of said transmission line, three single-phase devices of which the impedance has a reactive component counected in shunt across delta ohases of said u line, and means for so i: mg the reactive components of said devices as to maintain constant equal voltages on all of the delta phases.

The combination with th e polyphase conductors, of a plurality oi single-phase syiichronous dynamo-electric machines connected across dilierent delta phases of said conductors, said synchronous machines having wound damper windings, and means for causing the currents drawn by said synchronous machines to maintain a predetermined phase relationship between the d la voltages of said conductors. said meals cemprising means for associating said damper windings in series-circuit rela 'on ano electro-responsivc regulators V ciated with said synchronous machines for maintaining predetermined relative magnitudes of the single-phase voltages.

The combination with a three-phase line subject to unbalanced conditions, oi? three single-phase synchronous dyi' ino clectric machines having no material mechanical torque and having wound damper windings, means for connecting said machines in delta to said line, means for serially associating said damper windings in closed circuit and electro-responsive means for independently regulating said machines for constant line voltages.

7. The combination with a three-phase line subject to unbalanced conditions, of three single-phase synchronous dynamo-electric machines having no material mechanical torque and having wound damper windings, means for connecting said machines in delta to said line, means for serially associating said damper windings in closed circuit and electro-responsive means for independently regulating said machines for equal line voltages.

8. The combination with a three-phase line subject to unbalanced conditions, of three single-phase synchronous dynamoelectric machines having wound damper windings, means for connecting said machines in delta to said line, means for impressing such electromotive forces on said damper windings as to cause the currents therein to have llld Lil)

a predetermined relation to said unbalanced conditions and electro-responsivemeans for independently regulating said machines for constant line voltages 9. The combination with a three-phase line subject to unbalanced conditions, of three singlaphase synchronous dynamo-electricmachines having no material mechanical torque and having damper windings, means for connectin said machines in delta to said line, means itor maintaining the currentsin said damper windings at all times equal in all of said machines, and eleetro-responsive means for independently regulating said machines. 7 V

10. The combination with a polyphase line subject to unbalanced conditions, ofa plurality of single-phase synchronous dynamo ele'etric machines, connecting means associating said machines with said line, a shunt phase-balancer machine having its prie mary phases serially associated vwith said connecting means, respectively, and electros, responsive means for independently regulating said machines for constant line voltages.

11. The combination with a three-phase line subject to unbalanced conditions, 01 three single-phase synchronous dynamo-electric machines, connecting means associating said machineswith said line, a shunt phasebalancer machine serially associated with said connecting means, and electro-responsive f means for independently regulating said machines for constant line voltages.

12. The combination with a three-phase line subject to unbalanced conditions, or three single-phase synchronous dynamo-electrio machines having no material mechanical torque and having damper windings, means for connecting said machines in delta to said line, a shunt phase-balancer machine serially associated with said connecting means, means for mainta ning the currents 1n said damperwindings at all times equal in all of said sin 'lehase machines and electroresponsive means for independently regulating said single-phase machines for constant line voltages;

13. .The combination with: a polyphase 7 inc subject to unbalanced conditions, of a plurality of single-phase devices of which the impedance has a reactive component," each of said devices being capable otadpist ment from a maximum capacitive current component to a maximum inductive current component, means for connecting said devices to said line, a shunt phase-balancing devicevserially associated with said connecting means, and means responsive to the respective voltages across the corresponding phases of said line for varying said devices toward maximum capacitive current compo- 'sponsive'means for independently regulating said machines.

In testimony whereof, I have hereunto subscribed my name this 3rd day of June, 7

V JOSEPH" SLEPIAN. 

